Drill bit



J. L. REILLY DRILL BIT Feb. 27, 1940.

Original Filed Feb. 26, 1 936 Patented Feb. 27, 1940 DRILL BIT John L.Reilly, Claremont, Sullivan Machinery Company,

of Massachusetts N. 11., assignor to a corporation ApplicatlonFebruary26, 1936, Serial No. 85,778

- Renewed May 23, 1939 6 Claims.

My invention relates to drill bits, and is of particular adaptability,as will hereinafter appear, to detachable drill bits.

Ease of sharpening and re-sharpening' is of great importance withdetachable drill bits, as

such bits are very commonly used by contractors and others who have nodesire to go to the expense of purchasing forging machines for thepurpose of re-sharpening their drill bits. Users of detachable bits mayemploy, at relatively small expense, grinding devices for re-sharpeningtheir bits, and accordingly it is most desirable that a detachable bitbe capable of re-sharpening by a grinding device and with a minimum ofcomplication. If it is possible simply to move the bit bodilyrectilinearly towards a rotating grinding wheel while maintaining theaxis of the bit in a plane including the axis of rotation of the wheel,the simplest possible method of re-sharpening will be attained, as itwil be necessary only to move the bit forwardly along such a line to thenecessary degree, then to withdraw the bit and rotate it 180 on its axisand again feed it forward against the wheel. Such an operation alsoresults in a bit of very desirable construction and performancecharacteristics.

It is an object of my invention to provide an improved drill bit, andmore particularly to provide an improved drill bit very easy tore-sharpen, very fast cutting and very durable, and therefore especiallyadapted to detachable drill bit construction. It is another object of myinvention to provide a drill bit which can be sharpened 'with maximumease with the use of a single grinding wheel, and by relative movementbetween said' bit and the grinding wheel in a direction only normal tothe circles of rotation of the periphery of the grinding wheel. It is afurther object of my invention to provide a drill bit which may bere-sharpened also by a swinging movement of the grinding wheel about anaxis at right angles to the axial line of the bit. It is still anotherobject of my invention to provide an improved drill bit which will cutaway the stone very effectively across the inner portions of the holeand also chop away the stone at the outer edge or periphery of the hole,and through the use of chopping edges both reduce and compensate for anypossible wear of the extremities of the cutting edge or edges of thebit. Further objects and advantages of the invention will hereinaftermore fully appear.

In the accompanying drawing in which one form which my invention mayassume in practice has been illustrated:

Fig. 1 is a side view of the forward end of a drill bit constructed inaccordance with the illustrative embodiment of the invention.

Fig. 2 is a similar view taken at right angles to Fig. 1.

Fig. 3 is a front end elevation of the bit.

Fig. 4 is a section through the bit on the plane of the line 44 of Fig.1.

Fig. 5 is an axial section through the bit on the plane of the line 5- 5of Fig. 2.

Fig. 6 is a view showing the sharpening of a bit constructed inaccordancewith the invention, and

Fig. '7 is a sectional view showing a sharpening operation, the sectionbeing taken on the plane of the line 'I! of Fig. 6.

Referring now to the drawing, it will be observed that I haveillustrated my improved drill bit construction as embodied in adetachable drill bit I adapted to be suitably secured as by threads 2 tothe forward end of a drill steel shank. The drill bit is provided withpairs of diametrically opposite wings, the wings of one pair beingdisposed at right angles to the wings of the other.

Two of these wings, marked 3 and 4, may be narrower than the other wings5 and 6, but it is not imperative that this size relationship prevail.It is commonly desirable to provide for the supply of cleansing fluidthrough the drill bit to the bottom of the hole, and for that reason acleansing fluid supply passage I may be provided. Herein this is shownas opening through the forward end of the bit at the center thereof. Thewings 3 and 4 support cutting edges 8 and 9, these edges lying in acommon are, as illustrated at III in Fig. 1. Chopping edges II and [2are formed at or near the outer ends of the wings 6 and 5, thesechopping edges being preferably formed a small distance inside theextremities of these wings, as by bevelling at It, so that the risk offracturing or chipping oil the chopping edges wil be materially reduced.The forward end of the bit is formed by surfaces whose elements inplanes parallel to the diametric plane including the arc ID are allarcs. At right angles to these planes there are surface elements whichare straight lines, though that is not essential; As a result, it willbe noted that the forward surfaces i8 and IQ of the wings 6 and 5respectively are hollow ground, as it were. The opposite extremities ofthe cutting edges 9 and 8, denoted by and 2| in the drawing, will beobserved to project forwardly further than any other portions of thedrill bit, in the specific embodiment shown.

By appropriately determining either the diameter of the grinding wheel,or its radius of arcuate movement, or the radius of arcuate movement ofthe bit relative to the wheel, depending upon the method of sharpeningemployed, the curvature at x 22 at the periphery of the chopping wings 5and 6 may be caused to conform almost perfectly to the desired are, soto speak. That is to say, the chopping edge may be largely maintained ina cylinder whose diameter is equal to the'diametric istance between thepoints 20 and M. Different methods of re-sharpening and of initiallysharpening a bit of'this character may be employed. The peripheralsurface of the bit as at 23 may be msentially conical, and thesharpening of the bit may be accomplished as illustrated in Figs. 6 and'7 by the employment of a grinding wheel having frusto-conical grindingsurfaces 24 and 25, and advancing the bit toward the wheel along anaxial line 21, 26, thereby forming, say the surface I8 and thecorresponding surface 28 of the front of the bit, then withdrawing thebit along the line 26, 21 and turning it through 180 on its axis andagain advancing it toward the wheel, and thereby causing the surface 24of'the wheel to form the surface It and the surface 25 of the wheel toform the surface 29 of the bit, as shown in Fig. 6. For this operation,the diameter of the wheel should be made such that the curvature of theperiphery of the wheel will produce the desired curvature of the face ofthe bit.

A smaller wheel may be used, if desired, and the wheel may be swungabout 'an axis perpendicular to the axial line 26, 27 and in advance ofthe bit, the arcs of motion of the wheel conforming to the desired arcsto be formed on the surfaces i8, 28 and I9, 29; or the wheel may be heldstationary and the bit itself moved bodily about an axis forwardly ofthe bit, the path of the bit being then determined to produce thedesired curvature of the surfaces I8, 28 and I9, 29. Of course, ineither of the methods last described the bit will be rotated betweensuccessive grinding operations on its axial line. Of course annealingwould permit the use of milling cutters instead of grinding wheels, andthis falls within the contemplation of my invention.

The bit which results from these operations will obviously be a fastcutter, durable, despite the projection of the points 20 and 2H, becauseof the presence of the chopping edges 5 and 6, most easily re-sharpened,and highly desirable for the purposes for which it is intended. Aparticular advantage resides in the fact that the bit cuts a hole largerthan its own diameter, so that there results a hole larger than wouldcome from the use of prior standard forms of bit of the same gauges.

While I have in this application specifically described one form whichthe invention may assume in practice, it will be understood that thisform of the same is shown for purposes of illustration and that theinvention may be modified and embodied in various other forms withoutdeparting from the spirit or the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent is:

1. A drill bit having wings arranged in diametrically alined pairs, withthe diametric lines of said pairs at right angles to each other, one ofsaid pairs of wings having cutting edges extending radially therealongand the other of said wings having chopping edges at theouterextremities thereof, substantially the entireforwardendof said bitformed by surfaces struck on arcsaboutan axis in advance of said bit andsaid bit having a longitudinal section at its forward end, on adiametric .plane including such axis, terminating in a pair of forwardlyopening angles.

2. A drill bit having wings arranged in diametrically alined pairs withthe diametric lines of said pairs at right angles to each other, one

of said pairs of wings having diametrically alined edges in a common arestruck from a center in advance of the bit, said other wings havingadjacent their extremities arcuate chopping edges, and the forwardsurfaces of said bit between said diametrically alined edges and each ofsaid chopping edges conforming to frusto-conical surfaces struck aboutan axis disposed in advance of the bit and perpendicular to a lineincluding the bit axis.

3. A drill bit provided with chopping portions having arcuate choppingedges and concave forward chopping faces, and a cutting edge lying in adiametric line midway between said chopping edges, said cutting edge andsaid forward chopping faces being curved on arcs struck from centerswhich lie in a common straight line, and the extremities of said cuttingedge at the bit periphery projecting in advance of said chopping edges.

4. A drill bit having radially extending cutting edges and choppingedges disposed at opposite sides of the line including said cuttingedges, substantially the entire forward surface of said bit lying infour frusto-conical surfaces whose axes are alined and lie in a lineperpendicular to the bit axis extended, the outer extremities of saidcutting edges and the chopping edges lying substantially in a surface ofa cylinder whose axis is coincident with the bit axis.

5. A drill bit having wings arranged in diametrically alined pairs, withthe diametric lines of said pairs at right angles to each other, one ofsaid pairs of wings having alined edges in a common arc struck from acenter in advance of the bit, and the other pair of wings havingchopping edges which lie in the surface of a cylinder of a diametersubstantially equal to but slightly less than the distance between theextreme points in said alined edges and each of which also lies in asubstantially conical surface whose axis is perpendicular to the bitaxis extended.

6. A drill bit having wings of like radial dimension arranged indiametrically alined pairs with the diametric lines of said pairs atright angles to each other, one of said pairs of wings having alinededges in a common arc and said other wings having adjacent theirextremities arcuate chopping edges, the forward portions of the formerpair of wings terminating in and supporting said alined edges andconforming to surfaces of revolution whose axis is in advance of saidalined edges and perpendicular to a 7 plane including said alined edgesat a point in said plane through which the center line, extended, ofsaid bit passes, and the portions of said other wings inwardly of saidchopping edges cut back progressively towards the axis of the bit toprovide arcuate surfaces of revolution at the forward end of the lastmentioned wings whose axis coincides with the axis first mentioned andwhich arcuate surfaces extend to the rearmost portions of said firstmentioned surfaces of revolution, said bit symmetrical in centralsection on a plane perpendicular to said first mentioned plane, wherebythe complete forward end of said bit between said chopping edges maybeformed by effecting successive grinding relations of the portions of thebit at opposite sides of the alined edges with a generally vformed wheelalong lines radial of the wheel.

JOHN L. REIILY.

